Q:
You discuss calculating the distance and velocity of stars by
measuring the "red shift" of their visible light as they move
away from the Earth. It seems to me that you can only be sure
that the light is "shifting red," instead of "really red" if
you know the spectrum of a particular stars light prior to
the shift.

I have two questions:

1. How do you know what a particular star's light would look
like without the shift, so that you can calculate how much
shift has occurred, and then the star's distance and
velocity?

2. Do not visible portions of the electromagnetic spectrum,
for example microwave and X-rays, also exhibit a "red shift"
type of phenomenon? If so, what do you call and how do you
measure this?

A:
1. Astronomers compare the spectrum from an arc lamp, other
laboratory source, or some nearby star in which the spectral
lines t are precisely known.

2. All forms of light experience spectral shifts depending
on the their motion with respect to the observer. This shift
is independent of the wavelength of the light.